Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (hereinafter, referred to as “DASH”) (MPEG-DASH) using the same HTTP as browsing of a web site as an internationally standardized moving image delivery protocol available for moving image delivery via the Internet has been known (for example, see Non-Patent Literature 1).
DASH implements adaptive streaming technology. In other words, a content supply side is configured to prepare a plurality of streams in which content of the same subject is included, and an image quality, an angle of view size, or the like changes according to a communication environment of the Internet serving as a delivery path or a capability or a state of a reception side. On the other hand, the reception side can select an optimal stream among the plurality of streams prepared by the supply side according to the communication environment of the Internet, the decoding capability of the reception side, or the like and acquire and reproduce the selected optimal stream.
As described above, in the DASH, a metafile called a media presentation description (MPD) is delivered from the supply side to the reception side so that the reception side can adaptively select and acquire a stream.
An address (url information) of a supply source of streaming data (media data such as audio/video/subtitle) of content divided into chunks is described in the MPD. The reception side can access a server serving as a content supply source based on the url information, requests streaming data, and receives and reproduce streaming data HTTP-delivered according to the request.
In practice, the streaming data and the MPD are delivered to the reception side via a content delivery network (CDN) using the Internet.
FIG. 1 illustrates an example of a configuration of a content supply system that delivers content in a streaming manner based on the DASH.
A content supply system 10 includes a content supply device 20 of a side at which content is supplied and a plurality of DASH clients 30 of a side at which content is received. The DASH clients 30 are connected to the content supply device 20 via a CDN 12 using the Internet 11.
The content supply device 20 delivers content of the same subject through a plurality of streams having different bit rates. The content supply device 20 includes a content management server 21, a DASH segment streamer 22, and a DASH MPD server 23.
The content management server 21 manages content supplied to the DASH clients 30, generates a plurality of pieces of streaming data having different bit rates from content of the same subject, and outputs the generated streaming data to the DASH segment streamer 22.
The DASH segment streamer 22 temporally divides each piece of streaming data into segments, holds each of the segments as a file, and notifies the DASH MPD server 23 of an address of a supply source of the files. Further, the DASH segment streamer 22 HTTP-delivers the file of the segmented streaming data via the CDN 12 in response to a request (an HTTP request) from the DASH client 30 of the reception side as an HTTP server.
The DASH MPD server 23 generates an MPD in which, for example, an address indicating a supply source of files of (segments of) a plurality of pieces of streaming data is described, and HTTP-delivers the generated MPD via the CDN 12 according to the request (the HTTP request) from the DASH clients 30 of the reception side.
The DASH client 30 requests the DASH MPD server 23 to transmit the MPD, request the DASH segment streamer 22 to transmit the streaming data based on the MPD HTTP-delivered according to the request, and receive and reproduce the file HTTP-delivered according to the request.
A plurality of cache servers (not illustrated) that temporarily hold the MPD or the segment of the streaming data which is HTTP-delivered are provided on the CDN 12, and when the MPD or the segment that is held in advance is requested by the DASH client 30, the cache servers can HTTP-deliver the MPD or the segment held therein instead of the DASH MPD server 23 or the DASH segment streamer 22. In the CDN 12, since the cache servers are provided, the MPD or the segment can be efficiently HTTP-delivered to the plurality of DASH clients 30.
Hereinafter, an HTTP server (the DASH segment streamer 22) that HTTP-delivers the segment of the streaming data in direct response to the request from the DASH clients 30 is referred to as an origin server.